Valorization of shrimp waste by obligate alkaliphilic Bacillus marmarensis

Food wastes are one of the great deals of ever-growing world population. Among them, chitinous wastes are precious for being used as a substrate to produce value-added commodities. In the present work, the deproteinization of shrimp waste together with the production of alkaline protease enzyme by obligate alkalophilic Bacillus marmarensis was investigated. First, we determined optimum conditions including inoculum ratio, temperature, shrimp waste concentration, and fermentation time for alkaline protease production. The highest protease activity (269.48 ± 2.19 U/mL) was obtained with 5% sole shrimp waste pretreated by heating at 100 °C for 20 min at 35 °C and pH 10.0 with inoculum ratio of 6%. Under optimized conditions, B. marmarensis showed a deproteinization capacity of 70.62% at pH 10.0 and 56.52% at pH 12.0, respectively, and the Fourier transform infrared spectroscopy spectrum of chitin obtained from deproteinization by B. marmarensis presented the characteristics of chitin compared to literature. Furthermore, the production of alkaline proteases was performed by using different carbon and nitrogen sources in comparison with the enzyme produced solely from shrimp waste. Among the carbon and nitrogen sources used, the highest activity was obtained from sucrose together with peptone from meat as 239.87 ± 28.35 U/mL, which was lower than the activity obtained from sole shrimp waste. Thus, this work indicates that obligate alkalophilic B. marmarensis can be used to develop sustainable bioprocess to produce alkaline proteases from sole shrimp waste and deproteinization of it. To our knowledge, this is the first work for the valorization of shrimp waste by obligate alkalophilic bacteria.